CN105795355B - A kind of method for improving soluble dietary fiber content in black bean skin - Google Patents

Abstract

The invention discloses a method for increasing the content of soluble dietary fiber in black bean hulls. Specifically, the present invention provides a method for increasing the content of soluble dietary fiber in black bean hulls, comprising the steps of: (i) providing a black bean hull; (ii) ) under alkaline conditions, the black soybean hulls are mixed with an alkaline solution to obtain a first mixed solution, wherein the concentration of the alkaline hydrogen peroxide solution is 8-30%; and (iii) drying step (ii) The obtained first mixed solution can obtain the modified black bean husk with increased soluble dietary fiber content. The average soluble dietary fiber obtained by the method of the present invention is as high as 16.15%.

Description

A kind of method for improving soluble dietary fiber content in black bean skin

technical field

The invention relates to the field of biotechnology, in particular to a method for increasing the content of soluble dietary fiber in black bean hulls.

Background technique

Black bean is the black seed of legume soybean, and black bean skin is generally a waste from the food industry. Previous research on black bean skin has focused on the extraction and properties of black bean skin pigments, such as anthocyanins, red pigments, and some glycosides. It has also been reported that it can improve the absorption of iron in the body. However, there are few research reports on the direction of dietary fiber in black bean hull.

Dietary fiber is a carbohydrate that hardly produces heat. Its essence is that carbohydrates cannot be decomposed by human digestive enzymes. Polysaccharides have certain physiological functions, such as lowering blood lipids, regulating blood sugar, preventing colon cancer, and regulating the body. immunity, etc. Dietary fiber can be divided into soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) according to its water solubility; many studies have shown that soluble dietary fiber not only has better physicochemical properties, but also in many respects is more stronger physiological functions. Therefore, the current researches on the modification of dietary fiber mostly focus on improving the content or extraction rate of soluble dietary fiber, and the methods often used include enzymatic modification, chemical modification and physical modification.

Among the commonly used dietary fiber modification methods, the enzymatic method is relatively mild, but the cost is high and the efficiency is low; chemical modification may cause residues; physical modification requires large-scale equipment, such as ultra-high pressure equipment, blasting and extrusion equipment, etc. . Since most of the dietary fibers contained in black bean hulls are insoluble dietary fibers, there is an urgent need in the art to develop a method for increasing the content of soluble dietary fibers in black bean hulls.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for increasing the content of soluble dietary fiber in black soybean hulls.

A first aspect of the present invention provides a method for increasing the content of soluble dietary fiber in black bean hulls, comprising the steps of:

(i) providing a black bean husk;

(ii) under alkaline conditions, the black bean hulls are mixed with an alkaline solution to obtain a first mixed solution containing the black bean hulls and the alkaline solution, wherein the mass concentration of the alkaline solution is 8- 30%; and

(iii) drying the first mixed solution obtained in step (ii) to obtain the modified black soybean skin with increased soluble dietary fiber content.

In another preferred example, the black bean hulls are ground black bean hulls.

In another preferred example, the black bean hulls are black bean husks that have passed through a 40-mesh sieve.

In another preferred example, in step (ii), the pH of the alkaline condition is 8-13, preferably 9-12, more preferably 10-12.

In another preferred example, in step (ii), the alkaline solution is selected from the group consisting of hydrogen peroxide solution, sodium hydroxide solution, or a combination thereof.

In another preferred embodiment, the alkaline solution includes hydrogen peroxide solution.

In another preferred example, in step (ii), the solid-liquid ratio of the black bean hulls and the alkaline solution is 1:10-1:20, preferably 1:11-1:19, more preferably, 1:12-1:18.

In another preferred example, the mass concentration of the alkaline solution is 10-20%, preferably, 12-18%, more preferably, 14-16%, and most preferably, 15%.

In another preferred embodiment, the step (ii) further comprises the step of stirring at room temperature.

In another preferred embodiment, the stirring time is 0.1-5h, preferably 0.3-3h, more preferably 0.5-1h.

In another preferred example, the step (iii) further includes the steps of adjusting the pH of the first mixed solution to be neutral (pH is 6-8) and suction filtration.

In another preferred example, in the step (iii), the pH of the first mixed solution is adjusted to neutrality with an acid.

In another preferred embodiment, the acid is selected from the group consisting of hydrochloric acid, sulfuric acid, acetic acid, or a combination thereof.

In another preferred example, the filter residue obtained after the suction filtration is washed with pure water 2-20 times (preferably, 5-15 times, more preferably, 10 times) the quality of the black bean hull.

In another preferred example, the method further includes step (iv): detecting the content of soluble dietary fiber on the modified black soybean skin with increased soluble dietary fiber content obtained in step (iii).

It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described in the following (eg, the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, we will not repeat them here.

Description of drawings

Fig. 1 shows the comparison chart in terms of quality of the soluble dietary fiber (SDF) extracted from the black soybean skin modified by the alkaline hydrogen peroxide modification method of the present invention and the SDF extracted from the black soybean skin as it is (that is, not modified). Among them, A is the SDF extracted from the black bean husk as it is; B is the SDF extracted from the black bean hull after modification.

Detailed ways

Through long-term and in-depth research, the present inventor unexpectedly found a method for increasing the content of soluble dietary fiber in black bean hulls. % alkaline solution (such as hydrogen peroxide solution), the soluble dietary fiber content in the modified black bean skin obtained after suction filtration and drying is as high as 16.15% on average, and even higher can reach 17.34%. On this basis, the inventors have completed the present invention.

Soluble Dietary Fiber (SDF)

As used herein, "soluble dietary fiber" refers to that part of the meal that cannot be digested by digestive enzymes secreted by the human digestive tract, but is soluble in warm or hot water, and its aqueous solution can be reprecipitated by four times the amount of ethanol fiber. Soluble dietary fiber can play a more metabolic role in physiological function than insoluble dietary fiber. It has a significant effect in promoting the growth of probiotics in the intestine, preventing coronary heart disease, arteriosclerosis, hyperlipidemia, diabetes, obesity and other related diseases.

solid-liquid ratio

As used herein, the "solid-to-liquid ratio" refers to black soybean hull mass (g): solution volume (mL) of H ₂ O ₂ at a certain pH value and a certain concentration. In the present invention, the solid-liquid ratio is 1:10-1:20, preferably 1:11-1:19, more preferably 1:12-1:18, the modified black beans obtained The skin is high in soluble dietary fiber. In a preferred embodiment, when the solid-liquid ratio is 1:18, the soluble dietary fiber content in the obtained modified black bean hulls is the highest, up to 17.34%.

The main advantages of the present invention include:

(1) In the present invention, the dietary fiber of black bean hull is modified by the alkaline hydrogen peroxide method for the first time.

(2) By the method of the present invention, the measurement and extraction rate of soluble dietary fiber in black bean hulls is greatly improved from the original (that is, the black bean hull is directly extracted and measured for the content of soluble dietary fiber without any treatment) from 7.85% to 7.85%. 16.15% (even up to 17.34%).

(3) The method of the present invention is a chemical modification method with simple operation, low cost, no need to use large-scale instruments and no residue. At the same time, the glycosidic bonds of insoluble macromolecular polymers such as cellulose and insoluble hemicellulose are broken, and converted into soluble dietary fiber, thereby increasing the content of soluble dietary fiber (SDF) in the black bean husk, that is, the present invention develops a The new source of soluble dietary fiber also improves the utilization of food industry waste, turns waste into treasure, and reduces the output of industrial waste.

(4) The hydrogen peroxide used in the present invention is a clean and efficient oxidant, which can be decomposed into oxygen and water, and has no residual problems caused by other chemical modifications. In addition, alkaline hydrogen peroxide has a bleaching effect, which can improve the color state of black bean hull and black bean hull soluble dietary fiber, thereby improving its sensory quality.

In addition, the operation method of the present invention is relatively simple, does not involve large-scale instruments and equipment, and has low cost.

Extraction method of soluble dietary fiber (SDF) from black bean skin

(1) Sample enzymolysis:

①Accurately weigh (1.000±0.005) g of the sample and place it in a tall beaker.

② Add 40 mL of MES-TRIS buffer to the beaker, and stir on a magnetic stirrer until the sample is completely dispersed (to prevent the formation of clumps, so that the test substance and the enzyme can fully contact).

③ Enzymatic hydrolysis treatment with thermostable amylase: add 100 μL of thermostable amylase solution and stir at low speed. Cover the beaker with aluminum foil and react in a water bath at 95-100 °C for 30 min (the initial water bath temperature should reach 95 °C).

④ Cooling: All beakers were removed from the water bath and aired to 60°C. Open the aluminum foil cover, and use a spatula to scrape off the mesh on the edge of the beaker and the glue at the bottom of the beaker, so that the sample can be completely enzymatically hydrolyzed. Rinse the beaker walls and spatula with 10 mL of distilled water.

⑤ Enzymatic hydrolysis with protease: Add 10 μL of protease solution to each beaker. Covered with aluminum foil, the reaction was continuously shaken at 60°C for 30min (the temperature of the water bath at the beginning should reach 60°C) to make it fully react.

⑥ pH measurement: After 30min, open the aluminum foil cover and add 5mL of 0.561mol/L HCl to the beaker while stirring. At 60°C, use the solution or 1 mol/L HCl solution to adjust the final pH to 4.0-4.7 (check and adjust the pH when the solution is 60°C, because the pH will be higher at lower temperatures).

⑦ Enzymatic hydrolysis treatment with amyloglucosidase solution: add 100 μL amyloglucosidase solution while stirring. Cover with aluminum foil and continue shaking at 60 °C for 30 min, the temperature should be constant at 60 °C.

(2) Extraction and determination

Three layers of filter paper were laid on the Buchner funnel, and the filter paper was completely adsorbed on the surface of the Buchner funnel by moistening with water and pumping air. Filter the enzymatic hydrolysate and rinse the beaker, wash the residue twice with 10 mL of 70°C water, then filter again, transfer the entire filtrate to a 600mL tall beaker, and add about 4 times the amount of the filtrate to 95% ethanol that has been preheated to 60°C. Precipitate for 1 h at room temperature. After the pellet was centrifuged, the pellets were pooled and lyophilized. The lyophilisate is SDF.

Embodiment 1 Alkaline hydrogen peroxide modification method of the present invention

(1) Experimental method:

1. Pick the black bean skin to remove weeds and black beans;

2. Grind the black bean skin and pass it through a 40-mesh sieve;

3. Prepare an alkaline hydrogen peroxide solution of pH9-11 with a mass concentration of H ₂ O ₂ of 10%-20%, mix with the above-mentioned black bean husks at a material-to-liquid ratio of 1:12-1:18, and mix with a magnetic stirrer at room temperature The upper reaction is 0.5-1.5h;

4. After the reaction, the pH is adjusted to neutral (pH6-8) with hydrochloric acid;

5. Suction filtration, the filter residue is washed twice with pure water 10 times the quality of black bean hull powder;

6. The above-mentioned filter residues are placed in a 55°C oven for drying, for later use.

7. Referring to the national standard GB/T 5009.88-2008 method, the content of soluble dietary fiber (SDF) was determined on the modified black bean hulls.

(2) Optimization of modification conditions

Four variables _were selected for optimization, namely H2O2 concentration, pH, reaction time, solid _- liquid ratio, and the factor levels are shown in Table 1.

Table 1 Factor level table

The L ₉ (3 ⁴ ) orthogonal table was used to conduct the orthogonal test, and the results are shown in Table 2.

Table 2 Orthogonal test results and analysis of SDF extraction from black soybean skin treated with H ₂ O ₂

It can be seen from Table 1 and Table 2 that pH is the most important factor, followed by H ₂ O ₂ concentration, and the material-liquid ratio has the smallest influence. When the following conditions are selected: pH is 10, 20% H ₂ O ₂ , When the reaction time was 0.5h and the ratio of solid to liquid was 1:18, the average extraction rate of SDF was the highest, reaching 17.34%.

The comparative result of embodiment 3 and other modification methods

(1) HCl-ethanol modification method

5 g of each sample was weighed and soaked in 50 mL of HCl-ethanol with different concentrations for 3 days. The solution was made neutral with NaOH solution (10M). After filtering, the filter residue was washed twice with 50 mL of 95% ethanol. The washed filter residue was dried in an oven at 60°C for later use. The modified SDF was extracted by the extraction method of Example 1, and the SDF extraction rates after treatment with different concentrations of HCl-ethanol solutions are shown in Table 3.

The results showed that the extraction rate of SDF was partially improved under the extremely high HCl-ethanol concentration, but only reached about 10%, and it was found in the experiment that at the high HCl-ethanol concentration of 23.04%, the black bean hulls had been excessively degraded. It is too severe to be used as a method for modifying dietary fiber from black bean hulls.

Table 3 Effects of different concentrations of HCl-ethanol solution on the extraction rate of soluble dietary fiber from black soybean hulls

(2) Enzymatic modification

Weigh 4 g of black bean hull powder, add 40 mL of citric acid-sodium citrate buffer with a pH of 4.5, add a certain amount of compound plant hydrolase (Viscozyme L), and shake the reaction in a water bath at 50 °C for 2 h. Heated to 95°C and inactivated for 5min. Suction filtration, and the filter residue was washed twice with 40 mL of 95% ethanol. Transfer the washed filter residue to a 60°C oven for drying and use for later use.

Weigh 4 g of black soybean hull powder, add 40 mL of citric acid-sodium citrate buffer with a pH of 5.0, add a certain amount of cellulase (Celluclast) 1.5 L, and shake the reaction in a water bath at 50°C for 2 h. Heated to 95°C and inactivated for 5min. Suction filtration, and the filter residue was washed twice with 40 mL of 95% ethanol. Transfer the washed filter residue to a 60°C oven for drying and use for later use.

The extraction method of SDF is the same as that in Example 1.

Table 4 Effect of Viscozyme L addition on the extraction rate of soluble dietary fiber from black bean hulls

Table 5 Effect of Celluclast 1.5L addition on the extraction rate of soluble dietary fiber in black bean hulls

The results are shown in Table 4 and Table 5. The results showed that the two enzymes, Viscozyme L and Celluclast 1.5L, had unsatisfactory enzymatic hydrolysis effects on black bean hulls, the increase of soluble dietary fiber after enzymatic hydrolysis treatment was not obvious, and the cost of enzymatic method was high, so enzymatic modification was not effective. Suitable for large-scale industrial production.

Example 4 Influence of the alkaline hydrogen peroxide modification method of the present invention on the quality of soluble dietary fiber (SDF)

The color of the soluble dietary fiber (SDF) extracted from the modified black bean hull by the alkaline hydrogen peroxide modification method of the present invention is significantly improved. ) turns light white, as shown in Figure 1.

The results show that the soluble dietary fiber (SDF) obtained by the alkaline hydrogen peroxide modification method of the present invention has better quality and is more favorable for application in the food industry.

All documents mentioned herein are incorporated by reference in this application as if each document were individually incorporated by reference. In addition, it should be understood that after reading the above teaching content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (11)

1. A method for increasing the content of soluble dietary fiber in black soybean hulls is characterized by comprising the following steps:

(i) providing black bean curd skin;

(ii) under an alkaline condition, mixing the black bean skin with an alkaline solution to obtain a first mixed solution containing the black bean skin and the alkaline solution, wherein the mass concentration of the alkaline solution is 12-18%; and

(iii) (iii) drying the first mixed liquor obtained in step (ii) to obtain a modified black soybean hull having an increased content of soluble dietary fibers;

and, the step (ii) further comprises a step of stirring at room temperature; the stirring time is 0.5-1 h;

and, the alkaline solution is an alkaline hydrogen peroxide solution;

the pH of the alkaline condition is 10-12;

the material-liquid ratio of the black bean skin to the alkaline solution is 1:10-1: 20.

2. The method according to claim 1, wherein in the step (ii), the feed-to-liquid ratio of the black bean hull to the alkaline solution is 1:11-1: 19.

3. The method of claim 2, wherein in step (ii), the feed-to-liquid ratio of the black bean hull to the alkaline solution is 1:12 to 1: 18.

4. The method of claim 1, wherein the alkaline solution has a mass concentration of 14-16%.

5. The method of claim 1, wherein step (iii) further comprises the steps of adjusting the pH of the first mixed liquor to neutral and suction filtering.

6. The method according to claim 5, wherein the pH of the first mixed solution is adjusted to neutral with an acid in the step (iii).

7. The method of claim 6, wherein the acid is selected from the group consisting of: hydrochloric acid, sulfuric acid, acetic acid, or a combination thereof.

8. The method as claimed in claim 5, wherein the filter residue obtained after the suction filtration is washed with pure water 2-20 times the mass of the black soybean hull.

9. The method as claimed in claim 8, wherein the filter residue obtained after the suction filtration is washed with pure water of 5-15 times of the mass of the black soybean hull.

10. The method as claimed in claim 9, wherein the filter residue obtained after the suction filtration is washed with pure water of which the mass is 10 times that of the black soybean hull.

11. The method of claim 1, further comprising step (iv): (iv) detecting the content of the soluble dietary fiber in the modified black bean curd skin with the increased content of the soluble dietary fiber obtained in the step (iii).

Images